gritti 16 Flashcards
what’s the main difference between endocrine and exocrine glands?
no ducts are present in endocrine glands.
hormones are released into the blood stream directly.
autocrine signaling
the hormones will act on the same cell that has released them
Juxtacrine signaling
happens by cell to cell contact
a cell to receive the signal has to be in direct contact with the cell that has produced the signaling molecule (the molecule remains attached to the cell’s surface)
paracrine signaling
the hormones act on short distances (neighboring cells) but not cell to cell direct contact
classical endocrine signaling
the hormones are released into the blood stream and they reach organs that are far from hormones releasing cells
endocrine cells are from which origin?
epithelial origin
what do steroid hormones derive from?
cholesterol
what is the rate limiting step in steroid hormones synthesis?
pregnenolone
serotonin and melatonin derive from which amino acid?
tryptophan
histamine derive from which amino acid?
histidine
eicosanoids are hormones derived from?
-fatty acids
-in particular from arachidonic acid (except some exceptions)
prostaglandins are hormones derived from?
a fatty acids-derived type of hormones
each pancreatic islet is composed of
alpha cells->glucagon
located peripherally
beta cells->insulin
located centrally
delta cells->somatostatin
scattered, less abundant
these cells can not be distinguished in an H and E staining
parasympathetic and sympathetic fibers within an islet of langheran
sympathetic
stimulate glucagon release
parasympathetic
stimulate both glucagon and insulin release
enterochromaffin cells
present in both the islets and in ducts in the pancreas.
primary source of serotonin which participates in the overall regulation of the endocrine function of this organ
pituitary gland
-at the base of the brain
-divided in
1. neurohypophysis (derives from nervous system) and is connected to the hypothalamus by the infudibular stalk
- adenohypophysis (derives from the oral ectoderm, upgrowth invagination of the primitive oral cavity)
histologically you can tell that they have different embryological origins
neurohypophysis and adenohypohphis are divided in different pars:
neurohypophysis
pars nervosa
adenohypophysis
pars distalis (bigger one)
pars tuberalis (wraps around the infundibulum)
pars intermedia (boundary between Adeno and neuro hypophysis)
hypothalamic hypophyseal tract, what is it?
a vessel system that covers the neurohypophysis
take up all the peptides and hormones produced in the posterior pituitary and bring them to the target organs through circulation
hypothalamic hypophysisal portal system, what is it?
2 different group of vessels that come from the carotid artery.
one covers the infundibular stalk
the other one takes up the hormones produced in the adenohypophysis and bring them to the target organs through circulation
which types of cells can I find in the adenohypophysis?
LEARN THEM
chromophobes
do not secrete hormones
-pailed stained
chromophils
hormones secreting cells
-acidophils
stained in pink
1. somatotrophin cells that produce somatotrophin (growth hormones that act on bones and on the liver) lactotrophic cells that produce prolactin that acts on the mammary glands
-basophils
stained in blue/purple
-corticotropic cells that produce adrenocorticotropic hormone that act on the adrenal cortex
-gonadotropic cells that produce sex hormones (FSH, LH)
-thyrotropic cells that produce thyroid stimulating hormone that act on the thyroid gland
what is the peculiarity of the pars intermedia in the adenohypophisis?
the presence of protein-filled cysts
somatostatin released in the hypothalamus inhibits the production of?
TSH and somatotropin
dopamine released in the hypothalamus inhibits the release of?
prolactin
neurohypophisis cell composition
non myelinated axons that come from neurons with the cell body in the hypothalamus.
NB: HORMONES- SECRETING NEURONS
around the axons there are pituicytes cells as structural support
hormones secreted by the posterior pituitary
antidiuretic hormones (act on the kidney)
oxytocin (act on the uterus)
are hormones released from the neurons in the posterior pituitary free?
no, they are bonded to proteins called neurophysin I and II
herring bodies of the posterior pituitary
enlargement of the axons where hormones accumulate
hormone neurophysin complex
hormones when released by the hormones releasing neurons in the posterior pituitary are bonded to neurophysin 1 and 2
adrenal glands
on top of the kidneys
covered by a connective capsule
inner part: medulla
comes from the neural crest
outer part:cortex
comes from the mesoderm
the cortex is divided in three
zona glomerulosa
zona fascicolata
zona reticularis
which hormones are produced in the medulla of adrenal glands?
peptide hormones
(somatostatin and substance P)
catecholamines (adrenaline and noradrenaline)
which hormones are produced in the cortex of adrenal glands?
production of steroid hormones
glucocorticoids, mineralocorticoids and androgens
zona glomerulosa of the cortex of the adrenal gland
-on the outside
-closely packed columnar cells with many vessels
-cells organized in glomeruli
-produce mineralocorticoids (aldosterone-osmotic balance in the kidney and corticosterone-stress hormone)
zona fascicolata of the cortex of adrenal glands
-cells organized in chords
-similar appereance as the zona glomerulosa
-secretion of glucocorticoids (cortisol)
important for carbs, protein and lipid intake
zona reticularis
-closest one to the medulla
-irregular appearance with lots of capillaries
-cells store lipids droplets
-secrete androgens
what’s the name of the cells in the adrenal medulla?
chromaffin cells that arrange in clusters around medullary veins
secrete catecholamines (adrenaline and noradrenaline->80% adrenaline, more abundant production)
-these cells are modified postganglionic neurons
-when acetylcholine binds to specific receptors, catecholamines are released
chromogranins
proteins bonded to catecholamines (that are stored in granules)
thyroid gland secretes
-tri-iodotyronine(T3)
-thyroxine (T4)
regulate the basal metabolic rate.
the secretion of these two hormones is regulated by the pituitary TSH-thyroid stimulating hormone
-calcitonin (regulates blood calcium level->secretion of it make calcium level to drop->the secretion is dependent to blood calcium level)
thyroid follicles
-where hormones are stored in the thyroid
-thyrocytes are the epithelial cells around the follicle: simple cuboidal epithelium
-colloid is present inside the follicle with a glycoprotein called thyroglobulin (precursor for active thyroid hormones)
-around the follicles there is reticular connective tissue with fenestrated capillaries to favor the entrance of hormones into the bloodstream
what’s the name of the cells in the thyroid that secrete calcitonin?
parafollicular cells
around the thyroid follicle
which cells secrete melatonin?
pinealocytes in pineal gland
corpora arenacea in pineal gland
concentration of mineralized salts and calcium in the parenchyma
cells present in the parathyroid gland
-oxyphil cells (derivatives of principal cells, appear with an eosinophilic cytoplasm)
-principal cells (granules with stored parathyroid hormone->regulates calcium blood level)
PTH and CALCITONIN: effects
PTH->increase blood calcium levels when released
calcitonin->decrease calcium levels when released
